We propose a placebo controlled, double-blind randomized experiment evaluating lithium carbonate, desipramine, methylphenidate and placebo as treatments for cocaine abuse in 80 chronic users. The study is designed to: 1) determine the relative general efficacy of the four pharmacologic treatments, in combination with psychotherapy, in alleviating or halting cocaine abuse; 2) evaluate the psychological characteristics (symptoms, personality, social functioning and diagnosis) of chronic cocaine abusers pre and post treatment; 3) explore the possible presence of a "central" withdrawal state via neuroendocrine evaluation (Prolactin, Growth Hormone) of chronic cocaine abusers pre and post treatment. The study will also examine the relationships between treatment success or failure and psychological characteristics in order to explore a possible approach to treatment based on a potential specific effficacy for each pharmacologic treatment in clinically distinct sub-populations.